The purpose of this project is to conduct statistical research and provide consultation to the Division for clinical trials, laboratory experiments, and epidemiological studies relevant to cancer prevention and control. Research problems under investigation include statistical models for monitoring prevention trials; design of nutritional cohort studies with a greater variation of nutrient intake; design of studies to calibrate dietary assessment instruments, allowing repeated assessments of two different instruments, one of which is unbiased; analysis of animal experiments relating dietary fat intake to mammary tumor incidence; use of Bayesian methods for monitoring clinical trials; studies on a large observational database of HIV-infected subjects with evaluation of natural history of disease; and the design of trials for the prevention of recurrence of polyps. Statistical consultation is provided to numerous studies including the NIH Women's Health Initiative Clinical Trial. The consultation has involved extensive contributions to study design, study analysis, and data monitoring. Work on cancer projection models previously reported as a separate Intramural Research Project (Z01 CN 00142 BB) has been transferred to an extramural support contract, although we continue to provide consultation on the project. A large database on Division-supported Human Intervention Studies (HINTS) is being developed. The content and format of the data collection instrument has been tested and full data collection will begin in FY97.